Description of Frequency Test Elmer Station

This station is where the builders test their boards following completion of the Local Oscillator amd Divider stages. It has a frequency counter and a dual-trace oscilloscope for verifying frequency and quadrature.

Resources

Tools

ItemQtyNotes
Vise or 3rd hand 1(hold board under test)

Instruments

ItemQtyNotes
Frequency Counter with range to 20MHz with leads 1
Dual Trace Oscilloscope 50 MHz with 2 probes1

Process for Local Oscillator Stage

  • LO: Frequency Counter

    Connect one lead of the Freq Counter to ground, the other lead to the hairpin lead of R17

    The frequency should read very close to 18.730 MHz (Values of plus or minus 5kHz are not uncommon, and depend upon the accuracy of the counter being used.)

  • LO: Scope

    Scope the Local Oscillator Output

    • Scope Setup:

      • Time/Div = 10 nS/div
      • Attenuation Ratio: Chan 1 = 10X (probes, too)
      • Volts/Div: Chan 1 = 1V/div
      • Trigger on Chan 1

    • Ground

      Connect the probe's ground lead to ground

    • Probe

      Probe the hairpin lead of R17

    • Result

      Wave form should be the 18.730 MHz sine wave at 4 to 7 V pk-pk

  • LO: Failure

    If this test does not provide the desired results, refer the builder to the rework station

Process for Dividers Stage

  • Verify Builder Checked Pin Voltages

    The builder's manual specifies that the builder should validate that the voltages on the Divider IC's pins are in spec. The frequency tests should not be performed until they are in spec.

  • Dividers: Frequency Counter

    • Connect the frequency counter's ground lead to the board ground
    • Probe the "clk-0" testpoint on the top of the board
    • The frequency should read very close to 4.6825 MHz (one quarter of the LO frequency)
    • Repeat for "clk-1" and look for the same value

  • Dividers: Scope

    Scope the clk-0 and clk-1 outputs

    • Scope Setup

      • Time/Div = 40 nS/div
      • Attenuation Ratio: Chan 1 and Chan 2 = 10X (probes, too)
      • Volts/Div: Chan 1 and Chan 2 = 5V/div
      • Trigger on Chan 1

    • Ground

      Connect both scope probe ground clips to the board ground

    • Probe

      Probe "clk-0" testpoint as channel 1, "clk-1" testpoint as channel 2 simultaneously

    • Adjust

      Adjust the vertical position so that both traces will be visible, one above the other

    • Result

      You should see two equal amplitude square ("squareish") waveforms, 90 degrees apart.

  • Dividers: Failure

    If this test does not provide the desired results, refer the builder to the rework station

Build Stages Supported